1. Field of the Invention
This invention relates to an apparatus for supplying a working beam to a working apparatus such as an exposure apparatus used for the manufacture of semiconductive circuit devices, and in particular to an apparatus for transmission a laser beam by the use of a plurality of reflecting mirrors.
2. Related Background Art
For example, as regards a working apparatus using an excimer laser as a light source, the laser and the working apparatus are often disposed in different chambers to protect the working apparatus from discharge noise produced from the laser, dust, etc.
In such a case, it is necessary to effect the transmission of the laser beam from the laser to the working apparatus.
As a prior-art transmitting apparatus, there is one as shown in U.S. Pat. No. 4,653,903 wherein the rectilinearly travelling property of a laser beam is utilized and the laser beam is reflected by a plurality of reflecting mirrors to thereby accomplish the transmission of the laser beam. These reflecting mirrors must all be very strictly adjusted in inclination or angle to accurately transmit the laser beam to the target. However, even the strictly adjusted reflecting mirrors may later get out of order for some reason or other. If the inclination or angle of the reflecting mirrors changes a little, the reflection angle error of the laser beam induced thereby will have a magnitude twice as great as the error angle of the reflecting mirrors. As a result, there has arisen the problem that eclipse or the like of the beam occurs. As the transmission distance becomes greater, the amount of said error tends to increase.